Securities (Amortized cost and fair value of securities) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Available-for-sale Securities
Available-for-sale securities, amortized cost basis	$ 628,527	$ 664,139
Securities available for sale, gross unrealized gains	2,746	11,967
Securities available for sale, gross unrealized losses	(19,122)	(997)
Available-for-sale securities, fair value	612,151	675,109
Held-to-maturity Securities
Securities held to maturity, amortized cost	277,224	269,783
Securities held to maturity, gross unrealized gains	1,538	4,251
Securities held to maturity, gross unrealized losses	(15,786)	(363)
Securities held to maturity, fair value	262,976	273,671
U.S. Government agency securities [Member]
Held-to-maturity Securities
Securities held to maturity, amortized cost	149,093	178,926
Securities held to maturity, gross unrealized gains	0	700
Securities held to maturity, gross unrealized losses	(13,108)	(363)
Securities held to maturity, fair value	135,985	179,263
Residential mortgage-backed securities [Member]
Held-to-maturity Securities
Securities held to maturity, amortized cost	16,793	23,827
Securities held to maturity, gross unrealized gains	1,055	1,889
Securities held to maturity, gross unrealized losses	0	0
Securities held to maturity, fair value	17,848	25,716
Agency CMOs [Member]
Held-to-maturity Securities
Securities held to maturity, amortized cost	103,361	49,051
Securities held to maturity, gross unrealized gains	385	1,587
Securities held to maturity, gross unrealized losses	(2,526)	0
Securities held to maturity, fair value	101,220	50,638
Corporate debt securities [Member]
Held-to-maturity Securities
Securities held to maturity, amortized cost	5,000	15,000
Securities held to maturity, gross unrealized gains	94	13
Securities held to maturity, gross unrealized losses	0	0
Securities held to maturity, fair value	5,094	15,013
Municipal securities [Member]
Held-to-maturity Securities
Securities held to maturity, amortized cost	2,977	2,979
Securities held to maturity, gross unrealized gains	4	62
Securities held to maturity, gross unrealized losses	(152)	0
Securities held to maturity, fair value	2,829	3,041
U.S. Government agency securities [Member]
Available-for-sale Securities
Available-for-sale securities, amortized cost basis	33,995	33,994
Securities available for sale, gross unrealized gains	0	19
Securities available for sale, gross unrealized losses	(3,623)	(252)
Available-for-sale securities, fair value	30,372	33,761
Residential mortgage-backed securities [Member]
Available-for-sale Securities
Available-for-sale securities, amortized cost basis	67,323	55,614
Securities available for sale, gross unrealized gains	12	1,596
Securities available for sale, gross unrealized losses	(2,274)	0
Available-for-sale securities, fair value	65,061	57,210
Agency CMOs [Member]
Available-for-sale Securities
Available-for-sale securities, amortized cost basis	500,312	547,641
Securities available for sale, gross unrealized gains	2,734	9,971
Securities available for sale, gross unrealized losses	(12,014)	(745)
Available-for-sale securities, fair value	491,032	556,867
Municipal securities [Member]
Available-for-sale Securities
Available-for-sale securities, amortized cost basis	26,897	26,890
Securities available for sale, gross unrealized gains	0	381
Securities available for sale, gross unrealized losses	(1,211)	0
Available-for-sale securities, fair value	$ 25,686	$ 27,271